Environmental heterogeneity imposed by photovoltaic array alters grassland soil processes

The anticipated expansion of photovoltaic (PV) energy production is likely to have major impacts on ecosystems globally. PV arrays alter the spatiotemporal availability of abiotic drivers, such as light and precipitation, creating discrete microenvironments. Plant responses to PV-induced environmental heterogeneity are increasingly well studied, suggesting spatially explicit patterns of phenology, photosynthesis, productivity, and community composition; however, potential differences in soil microbial processes across these microenvironments are relatively unknown.

To determine how PV arrays influence soil microbial processes, we leveraged an established single-axis tracking photovoltaic array in Colorado, United States, where agriculture and PV energy production are co-located. We conducted our experiment in a portion of the array dominated by a C3 grass (Bromus inermis) to investigate soil physiochemical properties, microbial community structure, and function across microclimates. Soil samples were collected during the growing season from each panel edge (i.e., east & west), beneath panels, between panels, and outside of the array. Soil physiochemical properties generally did not differ across microclimates, although organic matter was highest on the east panel edge, where aboveground productivity is consistently greatest. Soil microbial biomass C & N were highest beneath panels, while substrate induced respiration rates were highest on the east panel edge. Soil microbial community structure differed greatly between microclimates within the array and plots outside the array, with unique bacterial & fungal genera dominating each microclimate (e.g., the fungi, Xylaria, on the east panel edge). Hence, the presence of PV arrays will generate microclimates that alter soil microbial community structure and function in grassland ecosystems, potentially shifting carbon cycling and other ecosystem processes.